Android would be "impaired" if it shipped a general-purpose mail client rather than one designed specifically for Gmail?
It would be "impaired" if part of the setup process was to select an app store[0], a browser[1], and a maps app[1]?
That sounds more like "consumer empowerment" than "impairment" to me.
[0] Google Play, F-Droid, Amazon's app store, etc
[1] Just show that category of programs from the aforementioned app store